1. Field of the Invention
The disclosure relates generally to Universal Serial Bus (USB) devices, and, more particularly to USB devices supporting super speed and non-super speed connections for communication with a host device and related methods.
2. Description of the Related Art
With vigorous development of computers and communications industry, a special interface system standard called “Universal Serial Bus” (USB) is established for communication connection. USB is a serial bus standard for external apparatus connection, providing hot plug, plug and play and other related functions. Currently, the USB 2.0 standard provides three transfer rates: low-speed (LS), full-speed (FS), and high-speed (HS) transfer rates, which support: 1.5 Mbps; 12 Mbps; and 480 Mbps data rates, respectively. However, due to continued advanced technological development, the electronic apparatuses may require to quickly access data from external apparatuses and subsequently perform related operations.
Therefore, a next generation USB industry-standard, the USB 3.0 standard, was established by the USB Implementers Forum. The USB 3.0 standard allows employment of Super Speed (SS) data transfer and non-Super Speed (i.e. USB 2.0) data transfer simultaneously, wherein Super Speed data transfer supports up to a 5 Gbps data rate. A USB system may include a USB host device and a USB device. The USB host device therein is responsible for controlling the timing and direction of data transmission on the USB. The USB device serves as the peripheral of the USB system.
A USB device may try to establish link on Super Speed (SS) with the host device first and then switch to establish a non-Super Speed such as the HS/FS/LS link if the SS link can not be established. Generally speaking, SS link and HS link cannot be active concurrently for one USB device. In other words, only one of the SS or HS/FS/LS links can be active at one time for one USB device. To active SS link and HS link concurrently, a physically or logically hub device that supports both SS link and HS link must be provided. Implementation of the hub device, however, can increase the hardware cost and design complexity for the USB system.